Analysis Of Impact Coefficient Of Simply Supported Beam Of Highway Bridge Under The Vehicle-jumping Condition

It is well know that bridge roughness irregularity is a major fact which can cause random vibration of vehicle-bridge coupling among many factors which affecting the dynamic response of vehicle-bridge system.At present,in the simulation study of vehicle-bridge coupling,the vehicle-bridge system is generally assumed to be continuous contact,and the vehicle-jumping phenomenon generated when driving on irregularity bridge is less be considered.In reality,the vehicle will often be bumps and leaps when there is driving on the irregularity bridge.So,the vehicle is essentially an intermittent contact with bridge,that is,the bridge is subjected to the impact of multiple separation and fitting of the vehicle system.In this paper,take the vehicle-bridge contact as the direction,taking full considerate of the intermittent contact phenomenon,the vehicle-jumping numerical model and the discriminating conditions of the quarter and half-car model are established.The impact coefficient changes under the vehicle-fitting and vehicle-jumping conditions were compared,and the sensitivity of each parameter to the impact coefficient under the vehicle-fitting and vehicle-jumping conditions was compared by orthogonal test.Finally,based on the bridge detection,the applicability and necessity of the vehicle-jumping model are illustrated by comparing the test data with the numerical simulation results.The research shows that when the bridge pavement is evenness,the displacement curve of the vehicle-fitting is the same as that of the vehicle-jumping.It is reasonable to assume that the vehicle-bridge is close-fitting.When there is unevenness in the bridge pavement,the impact coefficient of the vehicle-jumping under the action of various factors is basically same as vehicle-fitting,but there are differences in the details.Especially under the same conditions,the impact coefficient of the vehicle-jumping is obviously increased compared with the vehiclefitting,and the increase is significantly related to the bridge roughness irregularity,the speed and the bridge span.The multi-factor orthogonal test results show that the sensitivity of the impact coefficient under the close-fitting and jumping conditions is not exactly the same,but the sensitivity of the bridge roughness level,vehicle mass,speed is relatively large.Under the condition of vehicle-jumping,the influence of the span and bridge roughness level on the impact coefficient is significantly higher than that of the vehicle-fitting condition.The comparison between the bridge test and the numerical calculation shows that when the bridge pavement is irregularity,the calculated value of the impact coefficient under the vehicle-jumping model is closer to the measured result,and the error is reduced by about 10% compared with the vehicle-fitting condition.In the study of the impact coefficient,the unevenness of the bridge pavement and the vehicle-jumping condition may be an important reason why the simulated value often appears smaller than the measured value.